One or more embodiments relate to a nonvolatile memory device and a program method and an erase method using the same.
Recently, there has been an increasing demand for nonvolatile memory devices which can be electrically programmed and erased and do not require the refresh function of rewriting data at specific periods.
A nonvolatile memory cell enables electrical program/erase operations and performs the program and erase operations by varying a threshold voltage when electrons are migrated by a strong electric field applied to a thin oxide layer.
The nonvolatile memory device typically includes a memory cell array in which cells for storing data are arranged in matrix form and a page buffer for writing data into specific cells of the memory cell array or reading data stored in specific cells thereof. The page buffer includes bit line pairs connected to specific memory cells, a register for temporarily storing data to be written into the memory cell array or reading the data of specific cells from the memory cell array and temporarily storing the read data, a sensing node for detecting the voltage level of a specific bit line or a specific register, and a bit line select unit for controlling whether to connect the specific bit line to the sensing node.
The memory cell of this nonvolatile memory device may experience a phenomenon in which, despite performing an erase operation, electric charges are trapped in the oxide layer and the floating gate with the increasing number of program/erase cycles. With the increasing number of program/erase cycles, the amount of the trapped electric charges also increases, resulting in an increased threshold voltage of the nonvolatile memory cell. Consequently, the program speed increases. In order to compensate for the increase in the trapped charges or the program speed owing to the increase in the number of program/erase cycles, it may be necessary to change a program voltage or an erase voltage.